technical question bank for (automation)

7/22/2019 Technical Question Bank for (automation)

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General

1. What is Automation?

Automation is delegation of human control functions to technical equipment for increasing productivity

better quality, reduced cost & increased in safety working conditions.

2. What are the different components used in automation?

The components of automation system include

Sensors for sensing the input parameters (T!, Thermocouple, "ressure, #low, $eve% etc

Transmitters for transmitting the raw signal in electrical form

'ontrol system which includes "$', !'S & "! controllers

)utput devices * actuators like drives, control valves.

3. What are the different control systems used in Automation?

"! 'ontroller based control system

"$' based control system

!'S based 'ontrol system "' +ased automation system

4. Explain PI !ased control system.

"! ("roportional ntegral !erivative is the algorithm widely used in closed loop control. The "!controller takes care of closed loop control in plant. A number of "! controller with single or multiple loop

can be taken on network. "! 'ontrollers are widely for independent loops. Although some logic can be

implemented but not much of sequential logic can be implemented in "!s.

". ifference !et#een P$% & 'elay ?

"$' can be programmed whereas a relay cannot.

"$' works for analog *)s such as "! loops etc. whereas a relay cannot "$' is much more advanced as compared to relay.

odifications in relay base circuit is difficult compared to "$'s

(. ifference !et#een P$% & %) ?

%)- The system uses multiple processors, has a central database and the functionality is distributed. That is

the controller sub system performs the control functions, the history node connects the data, the S nodegives reports, the operator station gives a good , the engineering station allows engineering changes to

be made.

P$%- The system has processor & *)/s and some functional units like basic modules, communication

modules and so on. 0ses a S'A!A for visuali1ation. 2enerally the S'A!A does not use a central database.

!'S is often used in the big plants where the redundancy level needed is more and the analog input used arehigh.

*. What is P% !ased control system ?

n "' based control system, the '"0 of computer acts as processor, the "' based cards are used for

connecting nput and )utput. The A acts as memory. ard disk is used as storage device. 'urrently this

systems are very useful when the large data is to be proceed with very high speed. n many cases for greateraccuracy we can use the real3time operating system.


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+. What is Encoder ?

A feedback device which converts mechanical motion into electronic signals. 0sually an encoder is a rotarydevice that outputs digital pulses which correspond to incremental angular motion. The encoder consists of a

glass or metal wheel with alternating clear and opaque stripes that are detected by optical sensors to produce

the digital outputs.

,. Which are the leadin- P$% proiders ?

The leading "$' providers include

ockwell Automation - Allen +radley (icrologi4, S$', "$', 'ontrol $ogi4

Siemens ( S5 677, S5 877 , S5 977

2rouppe Schneider - odicon ( :ano, icro, "remium, ;uantum

2< #anuc - =ersa, Series >7387, >7357

essung - :e4tgen

1/. Which are the leadin- %) proiders ?

The leading !'S providers include

?okogawa - 'S 8777 , 'S @777 (


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Instrumentation )ystem

12. What types of sensors are used for measurin- different parameters?

Temperature sensors C T!, Thermocouple, Thermister

"ressure Sensor C +orden Tube, +ellows, Strain gauge

#low sensor C "itot tube

$evel, 'onductivity, !ensity, "h

13. What is transmitter?

A transmitter is an electronic device that is generally mounted in the field in close pro4imity to a sensor. The

sensor (also known as a transducer measures a physical variable such as temperature or pressure and

outputs a very low level electronic signal. The basic function of the transmitter is to provide the correctelectrical power to turn on (or e4cite the sensor then to read the low level sensor signal, amplify it to a

higher level electrical signal and send that signal a long distance to a control or read3out device.

Since low3level electrical signals do not transmit long distances with great accuracy, installing a transmittergenerally gives a tremendous improvement in the accuracy of the information delivered to a larger control

system. Typically the output form the transmitter is 9367 mA or 73D7 =

14. Why 42/ mA preferred oer /1/ si-nal ?

The 73D7 = signal has tendency to drop because of line resistance. f the distance between sensor and input

card is more the signal will not properly represent the field value. The 9367 mA will travel a long distance

without dropping signal value.

1". Why 42/ mA preferred oer /2/ mA si-nal ?

ith 73 67 mA you can not distinguish between minimum field value and connection break. ith 9367 mAinternal circuit can distinguish between connection break of minimum value. :ormally when the value is

minimum the transmitter will give you 9 mA while in case of connection breakage it will give 7 mA.

1(. ifference !et#een 2 #ire 3 #ire and 4 #ire transmitter.n 6 wire transmitter the power and signal are transmitted through same cable.

n 8 wire transmitter the data signal and power are with respect to common ground.

n 9 wire transmitter two wires for power supply and two for signals.)nly current transmitters can be used as 6 wire transmitters.

1*. What is a 5)mart6 7ransmitter ?.

A ESmartE transmitter is a transmitter that uses a microprocessor as the heart of the electronics. n addition, a

ESmartE transmitter will output some type of remote digital communications allowing you to read and set3up

the device from a remote position.

1+. What is 8ield !us ?.#ieldbus is a general term for a digital only, high speed communications protocol. The key attribute to

#ieldbus communications is higher speed communications with the possibility of addressing multipletransmitters all on the same field wiring. The #oundation #ieldbus is a specific digital protocol that is often

shortened to Fust be called #ieldbus. )ther digital only communications such as "rofibus are also #ieldbus

protocols

1,. What is Actuator ?.

n a closed3loop control system, the part of the final control element that translates the control signal into

action by the control device.


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2/. Explain Wor9in- of '7s

esistance Temperature !evice works on the principles that the resistance of the material changes as itstemperature changes. Temperature is determined by measuring resistance and then using the T! esistance

vs Temp characteristic to detect temperature. Typical elements used for T! are :ickel, 'opper and

"latinum. "latinum is widely used in T!s because of accuracy. "T D77 means at 7 deg temp D77 ohms

resistance. A typical T! consists of a fine platinum wire wrapped around a mandrel and covered with aprotective coating (glass or ceramic.

21. 7emperature measurement ran-e supported !y '7s?

The T! work on temperature range betweenC6@7 to G@7 deg '.

22. Explain Wor9in- of 7hermocouple

Thermocouple consists of two strips or wires made up of different metals and Foined at one end. The

temperature at that Functure induces an electromotive force (emf between the other ends. As the temperature

goes up the emf also increases. Through standard charts and tables the corresponding temperature can befound out.

The relationship between the thermocouple output and the temperature is quite non linear. !ifferentmetallurgies produce different outputs. The different metallurgies and different lineararities result in different

thermocou7le designations such as EHE, EB,E, E:E, E$E, etc.

23. What is %old :unction compensation?

The industry accepted standard for the temperature at open end is 7 deg '. Therefore most tables and chart

make the assumption that the temp at open end is 7 deg '. n industry the open ends are always at actualroom temperature and not 7 deg '. The emf adFustment because of difference between the actual temp and 7

deg ' is referred as 'old Hunction 'orrection ('H 'orrection

24. 7emperature measurement ran-e supported !y thermocouple ?The thermocouple work on broad temperature range ie C657 to 6877.

2". %an I split my one 70% si-nal to t#o separate instruments?

:o. The T*' signal is a very low3level millivolt signal, and should only be connected to one device. Splitting

to two devices may result in bad readings or loss of signal. The solution is to use a IdualJ T*' probe, or

convert one T*' output to a 9367 mA signal by using a transmitter or signal conditioner% then the new signalcan be sent to more than one instrument

2(. What are the flo# measurin- instruments used in 8lo# measurement ?

!ifferential pressure meters

"ositive displacement

=elocity meters

2*. Explain #or9in- of differential pressure measurement ?

Suitable restriction placed in flow stream causes a differential pressure across it.As flow depends upon differential pressure (ead & area, so any of them or both can be varied for varying

flow.

2+. What are the components of differential flo# sensor ?

#or creating differential pressure - )rifice plate, =enturi Tube, #low :o11le , pitot tube


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#or measuring pressure - 03Tube anometers, ingC+alance anometer, !.". 'ell

2,. What type of pressure sensors used in pressure measurement?

anometers

+ourdon tubes

+ellow elements

!iaphragm elements

!" transmitters

3/. Explain #or9in- of differential pressure transmitters.

"rocess pressure is transmitted through isolating diaphragms and oil fill fluid to a sensing diaphragm. The

sensing diaphragm is a stretched spring element that deflects in response to differential pressure across it.The displacement of the sensing diaphragm, a ma4imum deflection of7.779 inch (7.D7 mm, is proportional

to the applied pressure. 'apacitor plates on both sides of the sensing diaphragm detect the position of the

diaphragm. The transmitter electronics convert the differential capacitance between the sensing diaphragmand the capacitor plates into a two3wire, 9367 mA dc signal and a digital output signal.

31. What is %ontrol ales ?

The control valve, commonly named the final control element of control contains a pneumatic device that

converts the control signal from the controller in action, regulating the flow.

32. What type of control ales used in the industry ?

): 3 )## S


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)uperisory %ontrol And ata Ac;uisition )oft#are < Wonder#are In7ouch

3(. What is )%AA ? 'ole of I0=I )%AA in Industrial Automation

S'A!A - Supervisory control and data acquisition

- an achine nterface - uman machine nterface

This acts as an operator station. The operator can monitor as well as control the process parameters from thisstations. Apart from online process data the operator will have access to historical and real3time trends,alarms and reports. The operator can give commands to control hardware for opening the valve, change the

set point, start the pump etc..

3*. What are 8eatures of )%AA soft#are ?

The common features of S'A!A include !ynamic process mimic, Trends, Alarm, 'onnectivity with

hardware, ecipe management etc.

3+. Applications of )%AA.

S'A!A systems has many applications right from industrial automation, power distribution to water

management.

3,. )ome of the leadin- leadin- )%AA companies

nvensys onderware nTouch

Siemens in'' (


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W < .N< is indow maker. This will start the development package in nTouch. 0sing this you can

you can develop the application.

43. 7ypes of Windo# ?

'eplace


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4,. )ecurity mana-ement

Security provides the ability to control whether or not specific operators are allowed to perform specific

functions within an application. Security is based on the concept of the operator Elogging onE to theapplication and entering a E0ser :ameE and E"assword.E (The application developer sets up each operator

with a E0ser :ame,E a pre3assigned E"asswordE and an EAccess $evelE via the Special*Security*'onfigure

0sers..command either in indowaker or indow=iewer.

hen a new application is created, the default E0ser :ameE is EAdministratorE with an access level of >>>>

(which allows access to all security commands.

"/. What is the use of )cripts in In7ouch ?

s a way of writing logic in nTouch. nTouch has its own instructions and way of writing program.Application - $inked to the entire application.

indow - $inked to a specific window.

Bey - $inked to a specific key or key combination on the keyboard.

'ondition - $inked to a discrete tagname or e4pression.!ata 'hange - $inked to a tagname and*or tagname.field only.

"1. What is drier ?

A software which allows a computer to access the e4ternal devices using com ports or communication cards.

"2. What is E ?

!ynamic !ata


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Pro-ramma!le $o-ic %ontroller General

"(. What is P$%?"$' means "rogrammable $ogic 'ontroller. t is a class of industrially hardened devices that provideshardware interface for input sensors and output control element. The field *p include element like limit

switches, sensors, push button and the final control elements like actuator, solenoid*control valves, drives

hooters etc"$' Senses the input through *" modules, "rocesses the logic through '"0 and memory and gives output

through output module.

"*. Applications of P$%

"$' can be used in almost all industrial application solutions right from small machine to large

manufacturing plants.


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(2. What is role of I0 modules ?


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*1. Gie examples of I0P and utput connected to P$%s

!igital *" ("ushbutton, Switches

Analog *" (Temp, "ressure, #low, $evel

!igital )*" (Solenoids valves, 'ontactors

Analog )*" ('ontrol =alves, Speed

*2. Explain )ource and )in9 %oncept ?

Sinking Source type modules gives out the current to the field digital devices while sink type modules drawcurrent when the device is in high state

Sinking C hen active the output allows the current to flow to a common ground.

Sourcing C hen active, current flows from a supply, through the output device and to ground.

*3. What is forcin- of I0 ?

#orcing the *)s means making the desired status of *) in "$'s irrespective of its status coming from the

field.n certain cases when there is problem in receiving field input *output, we can force the i*)s so that the logic

takes desired state.

*4. )can cycle of P$%"$'/s scan cycle follows following path Scan cycle of "$'

nput mage 0pdation

"rocess $ogic


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+/. eed of redundancy

n critical processes, it is important to run the plant without failure. n such case it is important to have

redundancy so that even if one system fails the redundant system can take care without affecting plant.

+1. 7ypes of redundancy

'"0 redundancy - n case of '"0 failure the standby '"0 takes care of the plant

"ower Supply redundancy - n case the power supply fails the standby power supply takes control of thesituation.'ommunication - ultiple communication channels are provided to take care of communication failure

*) edundancy - ultiple *) channels are provided to take care of input or output failure.

+2. What are components of redundant P$% system ?

Typical component on Schneider edundant "$'s

The backplane used is either 9 slot oL L slot with

"ower Supply

'ontroller with built3in odbus "lus and odbus ports

)ptional dual cable odbus "lus

)ptional fiber optic odbus "lus 'S ot Standby module

!ual cable emote *) ead

The master and Standby configuration must be identical

+3. %ommonly used Instructions in P$%s

Examine if %losed B@I%C < F F


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even when the rung continuity is lost.

7imer )tatus it

.E - (enable Specifies whether or not the timer instruction is enabled

. - (!one Specifies whether or not the accumulated value of the timer equals to the preset value of the

timer.

"rogramming instruction (Advance

', 'ompute, "!, ST, Sequencer, egister, T'


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Pro-ramma!le $o-ic %ontroller Allen radley

+". What are the P$% ran-es aaila!le in 'oc9#ell ?

"ico - :on modular small "$'s

icrologi4 D777, D677 and D@77 Series

S$' - S$' @*7D, @*76, @*78 U.

'ontrol $ogi4 #le4 $ogic and Soft "$'

+(. What are the soft#are Dsed #ith A ?

#or "ico soft for "ico "$' programming

S $ogi4 @77 for icrologi4 and S$' "$'s programmingS $ogi4 @777 for 'ontrol $ogi4 "$'s programming

S'A!A 3 S =iew earlier 'ontrol =iew

+*. What is use of ') $inx soft#are ?

S $in4 software is used to perform following tasks. 'onfigure communication drivers

=iew configured drivers and active nodes


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,3. What are the arious communication interfaces supported !y A ?

The commonly used communication protocon in A+ includes !M, !9G@, =4+" eice et %ontrol net

+aud rate ma4 687.9 kbits*s D>.6 kbit*s @77 kbit*s @ bit*s

:o. of ma4.

nodes

L9 86 L9 >>

:etwork $ength 8.79G km D.6 km 7.9G5 km 87 km


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Pro-ramma!le $o-ic %ontroller )iemens

,+. What are the arious P$% system in )IA7I% )* ran-e ?

Siemens has broadly 8 "$' ranges ie Siemens S5 677 , 877 and 977

,,. What are the soft#are used #ith )iemens ?#or S5 677 "$' programming icrowin#or S5 877 and 977 system - Simantic S5 manager

The S'A!A software used by Siemens is in ''..


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1/2. Explain the 7ime )tamp aaila!le in )*2// P$% ?

This warning message indicates that the timestamps for the proFect do not match the timestamps for the

program in the "$'. This may indicate that the programs are different, in which case it would be dangerousto continue the current operation. owever, the programs may be functionally identical and still have

different timestamps.

1/3. What are the 7ime )tamps aaila!le in )*2// P$% ?

your program can monitor and evaluate. At startup, the "$' reads the *) configuration and stores thisinformation in the S memory. !uring normal operation, the *) status is periodically updated and stored in

the S memory. f the "$' detects a difference in the *) configuration, it sets the configuration3changedbit of the module3error byte% the *) module will not be updated until this bit is reset. #or the "$' to reset

this bit, the module *) must once again match the *) configuration stored in the system data memory.

'untime pro-rammin- errorsare non3fatal error conditions created by you or your program while the

program is being e4ecuted. An e4ample of this is an indirect3address pointer, which was valid when the

program compiled, modified by program e4ecution to point to an out3of3range address. 0se the "$' Y

nformationU command to determine what type of error has occurred.


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?ou can correct run3time programming errors only by modifying the user program. The run3time

programming errors are cleared at the ne4t transition from ST)" to 0: mode.

%ompile errors Bor pro-ramcompile errorsCare detected at download as the "$' compiles the program.

f there is a compile error, the compile halts, and the previous program (which is known to be valid since it

previously compiled is retrieved. All of these steps occur while the "$' is in ST)" mode. 'ompile errorscan be displayed using the "$' Y nformationU command.

1/+. =o# 7o Writin- and 8orcin- utputs in )*2// P$% )7P ode ?

To enable rite and #orce functions while in ST)" mode, choose the !ebug Y rite3#orce )utputs inST)" menu command.

The S53677 "$'s support writing and forcing outputs (both analog and digital while the "$' is in ST)"

mode. As a safety precaution, you must specifically request this functionality to be enabled in ST


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A StopWD **And with StopWD 7.6.

A: ighW$evel **And :ot with ighW$evel 7.9.

K "umpWD **Assign result to "umpWD ;7.7.

:


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)* 3//

111. What is A!solute and )ym!olic Addressin- I )*K3// P$%?

n a ST


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The data for each specific motor (for e4ample, speed, runup time, total operating time are saved in different

data blocks. The !+ associated with the #+ when it is called determines which motor is controlled. ith this

technique, only one function block is necessary for several motors

113. What are )ystem 8unction are in )*K3// P$%?

)ystem 8unctions

A system function is a preprogrammed function that is integrated on the S5 '"0. ?ou can call the S#' inyour program. S#'s are part of the operating system and are not loaded as part of the program. $ike #'s,

S#'s are blocks Jwithout memory.ES5 '"0s provide S#'s for the following functions-

'opying and block functions

'hecking the program

andling the clock and runtime meters

Transferring data sets

Transferring events from a '"0 to all other '"0s in multicomputing mode

andling timeofday and timedelay interrupts

andling synchronous errors, interrupts, and asynchronous errors

nformation on static and dynamic system data, for e4ample, diagnostics "rocess image updating and bit field processing

Addressing modules

!istributed *)

2lobal data communication

'ommunication via nonconfigured connections

2enerating blockrelated messages

114. ifferences !et#een Instance ata loc9s and )hared ata loc9s

A shared data block is not assigned to a logic block. t contains values required by the plant or machine andcan be called directly at any point in the program.

An instance data block is a block that is assigned directly to a logic block, such as a function block. The

instance data block contains the data that were stored in a function block in the variable declaration table.

11". =o# to Exchan-in-0)#appin- odules in the %onfi-uration 7a!le in )*3//

f you using 'onfig to revise a station configuration and you want to e4change a module for one with a

new order number for e4ample, proceed as follows-D. 0se a drag3and3drop operation to drag the module from the ardware 'atalog window over the old

module that is already placed.

6. !rop the new module. To the e4tent possible, the new module assumes the parameters of the one thatwas already inserted.

This procedure is faster than e4changing modules by deleting the old module and then inserting the new one

and assigning parameters to it.

?ou can turn this function on or off in 'onfig by means of the menu command ptions L )ettin-s(E


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The following table describes the comple4 data types. ?ou define structures and arrays either in the variable

declaration of the logic block or in a data block.

ata 7ype escription!AT


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Profi!us

!ata Transfer C D6 bit*s,

!istance C 68 Bm with fibre optic cable

:umber of nodes C up to D6@

12/. What are the !loc9s used in )iemens ?Simantic S5 manager uses !+, )+, #', "+ and #+

)+s - !etermine the structure of the user program

ata loc9 - These are the blocks used by logic blocks in '"0 program for storing the data. !+/s doesnot

contain any instructions and it take up space in the user memory. The user program can access a data block

with bit, byte, word or double word operations.Global data block - These contains information that can be accessed by all the logic block in the user

program.

Instance data block- These !+s are always assigned to a particular #+.

8% 8unctions - t is a logic block without memory. An #' is always e4ecuted by calling in another block. #'is used either for returning a function value to a calling function or e4ecuting a technological function

Temporary variable belonging to #' are saved in local stack and this data is lost when the #' has beene4ecuted.

8unction loc9s B8sC < A function block is block with a memory. A #+ contains a program that is always

e4ecuted when a different logic block calls the #+. #+ make it much easier to program frequently occurring

comple4 functions.

121. What are )8%s and )8s ?

S#+s and S#'s are integrated in the S5 '"0 and allow you access to some important system functions.

122. What is )tatement $ist?

Statement $ist (ST$ is a te4tual programming language that can be used to create the code section of logic

blocks. ts synta4 for statements is similar to assembler language and consists of instructions followed byaddresses on which the instructions acts.

technical question bank for (automation)

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